The present invention relates to novel methods for producing certain 4- or 5-phenyl-pentenals, and lower alkyl or lower alkylene acetals, a number of which are novel themselves which are used to alter the flavor and/or aroma of consumable materials. The above-mentioned acetals may also act as precursors for their corresponding free aldehydes which alter the flavor and/or aroma of consumable materials.
There has been considerable work performed relating to substances which can be used to impart flavors and fragrances to various consumable materials. These substances are used to diminish the use requirement of natural materials some of which may be in short supply and to provide such uniform properties in the finished product. Citrus flavors, walnut flavors, chocolate flavors, cinnamon flavors, green vegetable flavors, watermelon flavors, cucumber flavors, green floral aromas, green twiggy aromas, and cinnamon aromas are particularly desirable for many uses in consumable materials.
3-Phenyl-pentenals have been suggested in U.S. patent application Ser. No. 43,555, filed June 4, 1970 now U.S. Pat. No. 3,694,232 for use in cocoa flavors whereby notes characteristic of milk chocolate are provided.
3-Phenyl-4-pentenal is indicated to cause the chocolate beverage to have a fuller, richer sweet milk chocolate flavor. U.S. Pat. No. 3,582,360 issued on June 1, 1971 discloses certain 2-phenyl-2-alkenals as being useful for preparing flavoring compositions and food compositions, particularly those having chocolate or cocoa flavors and/or aroma qualities. Thus, for example, the compound 5-methyl-2-phenyl-2-hexenal is indicated therein to alter imitation cocoa flavor so as to provide a more natural cocoa flavor and impart a character of bitter chocolate.
Acetals are shown to be useful in fragrance formulation at Column 2, lines 50-65 of U.S. Pat. No. 3,636,113. Such acetals have the structures: ##STR3## wherein R.sub.1 and R.sub.2 are either hydrogen or lower alkyl; wherein R.sub.3 and R.sub.4 are the same or different lower alkyl groups, and wherein n is 1 or 2 and lower alkylene cyclic acetals having the structure ##STR4## wherein R.sub.5 is lower alkylene.
In U.S. patent application Ser. No. 43,555 mentioned above, mention is made of the diethyl acetal of 3-phenyl-4-pentenal and the diethyl acetal of 3-phenyl-3-pentenal; but only as intermediates for producing 3-phenyl-3-pentenal and 3-phenyl-2-pentenal from 3-phenyl-4-pentenal.
In West et al. "Synthetic Perfumes: their Chemistry and Preparation", published by Edward, Arnold & Co., London, England, in 1949, on page 315 cinnamaldehyde dimethyl acetal is stated to "have a fine cinnamon-cassia odor which renders it useful in some Chanel-like fancy perfume and in oriental types like Tabac Blond and Fleur de Tabac". Cinnamaldehyde diethyl acetal is also reported. These materials have the following structures: ##STR5## wherein R is methyl or ethyl.
Cinnamaldehyde diethyl acetal is reported in "Perfume and Flavor Chemicals (Aroma Chemicals)" by S. Arctander (published by the author in Montclair, N.J. 11969) as having a "faint but fresh green slightly spicy oily sweet odor and a mild and oily sweet taste." Arctander goes on to state: "since this acetal -- like most other acetals -- is unstable under mildly acid conditions it finds little if any use in flavor compositions". In addition, Arctander also reports cinnamaldehyde 2,4-dihydroxy-4-methyl-pentane acetal as "soft, tenacious, natural, cinnamon type odor not nearly as harsh as cinnamic aldehyde yet rich and lasting as aldehyde itself". Cinnamic aldehyde dimethyl acetal is also reported by Arctander and with reference to this acetal Arctander states: "It should be noted that pure, aldehyde-free acetal is practically colorless and carries little or no odor similarly to the aldehyde". The ethylene glycol acetal of cinnamic aldehyde is indicated by Arctander to be useful in flavor compositions, such as all spice, cassia, cinnamon, clove and various spice blend and it is stated by Arctander to have a sweet spicy cinnamon all spice taste not quite as sweet as the aldehyde. It should be noted that cinnamic aldehyde ethylene glycol acetal is on the GRAS list and has been given F.E.M.A. No. 2287.
The cinnamic aldehyde acetals of the prior art are not considered to impart certain desired qualities to consumable materials which acetals of 4- and 5-phenyl-pentenals of this invention are capable of doing as more specifically described below.
The prior art cinnamic aldehyde acetal noted above, however, being unsaturated in a position .alpha.,.beta.- to the acetal moiety, are relatively unstable even in aqueous media.